A ray of light when refracted suffers change in velocity. In this context, which one among the following statements is correct ?

Refraction occurs because light travels at different speeds in different media [4]. The optical density of a medium is a measure of its ability to refract light, which is inversely related to the speed of light within it [1]. An optically denser medium has a higher refractive index compared to an optically rarer medium [5]. According to the principles of optics, the speed of light is higher in a rarer medium and lower in a denser medium [1]. Therefore, when a ray of light transitions from an optically rarer medium (like air) to an optically denser medium (like glass or water), its velocity decreases [2]. This change in velocity is the fundamental cause of the bending of light toward the normal during such a transition [3].

Sources

1. [4] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 159
2. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 149
3. [5] https://www.ncbi.nlm.nih.gov/books/NBK594230/
4. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
5. [3] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.10 > p. 147